ส่วนประกอบของไฟล์แอป SwiftUI

Every SwiftUI project has a file named after your app, like MyFirstApp.swift. This app file is the true entry point where your whole app begins. 📱

The @main attribute tells Swift exactly where your program starts. iOS launches your app by running the type marked with it.

Your main struct conforms to the App protocol. This is the SwiftUI blueprint for an application, describing what scenes it shows.

Inside the App struct, a body property describes your app's scenes. SwiftUI reads it to know what to display when the app launches.

The app's body returns a Scene, not a View. A scene is a container for a window or screen that holds your actual views inside it.

WindowGroup is the most common scene. It manages your app's main window and, on iPhone, simply fills the whole screen.

Inside WindowGroup you place your root view, usually ContentView(). It is the first screen the user sees when the app opens.

ContentView sits in its own file, separate from the app file. Keeping the entry point and the UI apart keeps your project tidy and clear.

The chain is simple: @main starts the App, the App shows a WindowGroup, and the WindowGroup displays your ContentView. ✨

An app can have just one @main entry point. The template already provides it, so you rarely add or change this part yourself.

You will spend most of your time editing views like ContentView, not the app file. The app file mostly just wires everything together.

You learned the chain: @main on the App struct returns a WindowGroup scene that shows ContentView. That is how a SwiftUI app boots up. 🧩